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A visualization technique of subsurface features with a nanometer-scale spatial resolution is strongly demanded. Some research groups have demonstrated the visualization of subsurface features using various techniques based on atomic force microscopy. However, the imaging mechanisms have not yet been fully understood. In this study, we demonstrated the visualization of subsurface Au nanoparticles buried in a polymer matrix 900 nm from the surface using two techniques; i.e., resonance tracking atomic force acoustic microscopy and contact resonance spectroscopy. It was clarified that the subsurface features were visualized by the two techniques as the area with a higher contact resonance frequency and a higher Q-factor than those in the surrounding area, which suggests that the visualization is realized by the variation of the contact stiffness and damping of the polymer matrix due to the existence of the buried nanoparticles.

Surface charge distributions on biological molecules in aqueous solutions are essential for the interactions between biomolecules, such as DNA condensation, antibody-antigen interactions, and enzyme reactions. There has been a significant demand for a molecular-scale charge density measurement technique for better understanding such interactions. In this paper, we present the local electric double layer (EDL) force measurements on DNA molecules in aqueous solutions using frequency modulation atomic force microscopy (FM-AFM) with a three-dimensional force mapping technique. The EDL forces measured in a 100 mM KCl solution well agreed with the theoretical EDL forces calculated using reasonable parameters, suggesting that FM-AFM can be used for molecular-scale quantitative charge density measurements on biological molecules especially in a highly concentrated electrolyte.

Surfaces of polymerized 2,4-hexadiyne-1,6 bis(p-toluene-sulphonate) (poly-PTS) single crystals were investigated on a molecular scale by noncontact atomic force microscopy (NC-AFM). Molecularly resolved images of the surface structures, the energy dissipation and the surface potential (SP) distribution were successfully obtained. The possible origins of energy dissipation are discussed in terms of the relationship with the molecular fluctuation. Furthermore, to ascertain the origin of the SP distribution, the obtained SP image was compared with the calculated local charges on the individual atoms forming the molecule.

We investigated alkanethiol phase-separated self-assembled monolayers (PS-SAMs) using the Kelvin probe force microscope (KFM) combined with the non-contact atomic force microscope (NC-AFM). PS-SAMs were composed of two species of different chain-length alkanethiol. The surface potential (SP) measurements showed that the value of SP was linearly increased as a function of the chain length and that the gradient was about 9 mV per CH2 unit. In addition, we succeeded in obtaining nanometre-scale variations of the SP, which were discussed in the context of the surface structures.

The nanoscopic ferroelectric domains could be formed in P(VDF/TrFE) thin films by applying electric pulses with a conductive atomic force microscope, and detected by using piezoelectric response, revealing that the directions of electric dipoles in organic molecules can be controlled in nanoscale. By changing the polarity of the applied pulses, temporally stable binary information could be `written' in these films. Moreover, the possibilities of the molecular manipulation and the creation of high-density molecular memory devices utilizing the electric interaction between the polar molecules and the scanning probe microscopy tips are discussed.

The scanning tunneling microscope (STM) is known for its high lateral resolution. The unreliability of the scanning and positioning motion of the STM were monitored by interferometer and capacitance recently. The widely used conventional lead zirconium titanate (PZT) tube scanner has good mechanical properties; however, the motion of the tube includes angular motion which generates large error. Even with an optical interferometer to calibrate STM tip motion, the angular motion reduces or eliminates the visibility of interference. We have developed an eight-segmented tube scanner which reduces angular motion for maintaining the visibility of interference and reduces Abbe error. The residual error of the value measured by a high-accuracy interferometer which measured the motion of the newly developed eight-segmented tube scanner was estimated by measuring a standard pattern. The accuracy of the interferometer, which used a balanced detection technique, the principle of which is also reported in this paper, was measured by a capacitance gauge.

We have developed a novel method for nanometer-sized droplet deposition of electrically conductive liquids based on the dynamic mode atomic force microscopy (AFM). We succeeded in depositing liquid droplets with a volume of ten zeptoliters or smaller and in making arrays of the droplets with a spacing of several tens of nanometers using the AFM cantilever with a small aperture fabricated by a focused ion beam. The liquid droplets were deposited through the aperture by applying an electric field between the liquid and a conductive surface.

Submolecular resolution viscoelastic imaging of a poly(2,4-hexadiyne-1,6-diyl bis(p-toluene-sulfonate)) single crystal was achieved using force modulation microscopy under ambient conditions. The elastic image clearly visualized the structure of p-toluene-sulfonate side chains. The viscotic image visualized that the phase delay on the main chains was smallest, while it became largest on the toluene rings in the side chains. The result is considered to be closely related to the molecular dynamics of the crystal.

We produced local polarized domains of ferroelectric P(VDF/TrFE) copolymer thin films on a carbon nanotube field-effect transistor (CN-FET) channel by atomic force microscopy (AFM). The drain current versus gate voltage (I(d)-V(g)) curves measured after forming the local polarized domains showed a shift in the threshold voltages. We also found that the amount of the shifts in the threshold voltages gradually decreased during the measurement of this characteristic over 100 h after forming the polarized domains. The mechanisms of the shifts in the threshold voltages and their decreasing behaviour were explained in terms of the excessive charges that were induced upon the formation of the polarized domains.

Topographic imaging or friction force imaging of a polymer lamella in molecular resolution using atomic force microscopy (AFM) is significantly disturbed by the existence of an amorphous layer on top of the crystal. In this paper, we report the first successful molecular imaging of a polymer lamella using force modulation microscopy (FMM), which is capable of imaging crystalline molecules even if the crystal surface is covered with an amorphous layer. Molecular chains of a poly(vinylidenefluoride–trifluoroethylene) (P(VDF–TrFE)) lamella under an amorphous layer were clearly imaged using FMM at room temperature in ambient conditions. The origins and mechanisms of the image contrast in molecular resolution are also discussed.

Surface potentials of single wall carbon nanotubes (SWNTs) connecting two metallic electrodes have been investigated by both Kelvin probe force microscopy (KFM) and atomic force microscope potentiometry (AFMP). By comparing the surface potential measurements obtained by both methods, we also studied the major factors affecting the potential measurements of the SWNTs, such as the surroundings, stray electric fields, and the effect of the AFM tip size, which can be larger than the SWNT diameter. In this study, we used KFM based on non-contact AFM and AFMP using the point-by-point contact mode in which the AFM tip worked as a voltage probe.